Field of the Invention
The invention relates to a guard device for a postage meter, especially for protecting an operator upon reaching into a mail or envelope feed mechanism.
Until now, printing in postage meters has primarily been carried out by inking rollers or thermal print heads. The individual letter is fed horizontally, resting on a conveyor belt, until it reaches the printing unit. A maximum slot width between the printing unit and the conveyor belt is 8 mm, so that the fingers of an operator cannot get caught, as is seen in German Patents DE 38 16 548 C2 and DE 41 14 963 C2 and German Published, Non-Prosecuted Patent Application DE 42 28 765 A1.
Recently, attempts have been made to exploit the advantages of ink jet printing in postage meter technology as well. The printing is carried out in a contactless manner with ink jet printing heads, as is seen in German Patent DE 44 24 771 C1 and German Utility Model DE 94 20 734 U1.
In that connection, a postage meter has been proposed in German Patent Applications DE 19 605 014 and DE 19 605 015, in which the letters are fed standing upright, tilted slightly backward, with the aid of a revolving conveyor belt. The letters rest on a guide plate in which a printing window is provided and in which the ink jet printing head is installed in a stationary manner. Contact-pressure elements secured to the conveyor belt press the letters against the guide plate and carry them along by friction. Except for a guide gap for the letters, the transport region is covered in such a way that the risk of an operator reaching in from above is prevented.
However, reaching in is still possible in the lateral exit region for the letters since the guide gap can have a width of up to 20 mm, although reaching in is not permitted according to the instructions for use. When the conveyor belt is in operation, a finger inserted from the side into the guide gap can become caught between a contact-pressure element and the lateral covering of the conveyor belt and can be squeezed, depending on the driving force. The driving force is dimensioned in such a way that even letters or packages with a mass of 2000 g are still securely fed. The clamping force in the transport direction is then correspondingly great. Slippage of the drive is precluded, since a toothed belt drive is employed. There is accordingly a need for safety provisions.
On the other hand, a device for printing markings on flat pieces of mail with one or more printing stations each having at least one print head are known, as is seen from German Published, Non-Prosecuted Patent Application DE 195 08 180 A2. The mail is moved upright past the printing stations, resting on a curtain or lever and clamped in place between a conveyor belt and a cover belt. Nothing is the about safety provisions.
Finally, a safety switch for removable guard hoods, doors or flaps is also known from German Patent DE 33 12 657 C2. The safety switch includes a switch housing and an actuator, which is insertable into the switch housing to reach a first switching position, that is a switch on position, and can be pulled all the way out of the switch housing to reach a second switch position, that is a switch off position. A switch member that is axially displaceable inside the switch housing is movable by the actuator.